This invention relates generally to the field of composite materials and more particularly to a method for composite material repair.
Many manufacturing processes today call for the fabrication of components from xe2x80x9ccompositexe2x80x9d materials, also known as fiber-reinforced polymers. Fiber-reinforced polymers are comprised of reinforcing fibers that are positioned in a polymer matrix. Commonly, the reinforcing fibers are fiberglass, although high strength fibers such as aramid and carbon are used in advanced applications, such as aerospace applications. The polymer matrix is typically a thermoset resin, such as polyester, vinyl ester, or epoxy. Specialized resins, such as, phenolic, polyurethane and silicone are used for certain applications.
Composite materials may be formed using numerous types of fabrication process. One such process is a wet lay-up process. In a wet lay-up process, layers of dry reinforcing fiber are laid on a mold by hand or by a placement machine. Liquid resin is then poured on the fiber materials such that the resin fills the spaces between the fibers. The materials may then be cured at room temperature or in an autoclave and the liquid resin turns into a solid thermoset. The fibers are thus embedded in the solid thermoset resin and reinforce the resin. Alternatively, layers of fibers can be pre-impregnated with resin and then partially cured to form layers of xe2x80x9cprepregxe2x80x9d material. After this partial curing, the resin has not completely set and the prepreg layers are flexible and can be shaped in or around a mold or forming tool. Once the prepreg layers are so shaped, the prepreg is then completely cured in an autoclave to form a fiber-reinforced laminate.
A common defect associated with composite structures is air inclusions or voids located inside the composite material. Such voids weaken the composite material and sometimes must be repaired. Another scenario requiring repair is when the composite material is impacted during service, resulting in delamination or delaminations between layers of the material. Such damage is typically referred to as interlaminar defects or interlaminar damage.
One type of repair for voids and interlaminar defects is resin injection. During one type of resin injection repair, two holes are drilled through the composite material to the void or delamination inside the composite material. The two holes are typically drilled at opposite ends of the defect. Resin is then either driven into one hole using pressure until it exits the second hole, or resin is drawn into one hole by applying a vacuum to the second hole. When using such a two-hole process, air entrapment in the void is common and therefore the resin does not completely fill the void. In addition, since two holes must be drilled in the structure, the already weak structure is further weakened.
In accordance with the present invention, a method for composite material repair is provided that substantially eliminates or reduces disadvantages or problems associated with previously developed methods. In particular, the present invention contemplates a method of repairing a void in a composite material using a repair material injected into the void through a single channel.
In one embodiment of the present invention, a method for repairing a composite material having an internal void includes identifying the location of the internal void and forming a single channel extending from a surface of the composite material to the internal void. The method further includes pulling a vacuum in the internal void and inserting a repair material through the channel into the internal void.
Technical advantages of the present invention include a method for composite material repair that provides an improved method of repairing voids in composite materials over the prior art. Unlike the prior art, the present invention only requires the formation of one hole or channel in the composite material, and thus minimal additional damage is caused by the repair process. Furthermore, the method of the present invention allows the creation of a complete or almost complete vacuum in the void, causing most of the air molecules to be removed from the void before the repair material is injected. Therefore, the amount of air remaining in the void after the repair material has been injected is minimized and the void is entirely or almost entirely filled with the repair material.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.